I'm not sure why the Thai Board of Censors has targeted my film, Syndromes and a Century. But it has. The board has demanded I cut four scenes before it can be released in my home country - seemingly innocuous moments of a young monk playing a guitar, a group of doctors drinking whisky in a hospital basement, a doctor kissing his girlfriend in a hospital locker room and two monks playing with a remote-controlled flying saucer.

Until I make those changes, the print of Syndromes will remain locked up at police headquarters, despite our promise not to show the movie if they hand the print back. The board just doesn't trust me and my colleagues. We could appeal against their ruling, but we have decided not to - the judges who would hear the appeal might find even more to object to.

It's not as if we are insulting monks and doctors - films that show them behaving much worse have been released here, and I'd thought Syndromes was a respectful film, a tribute to my parents (who were doctors). So why was my film locked away? One theory is that the major studios have too much influence over what gets shown. Only one or two films are released each week in Thailand, so there's a lot of competition for those slots - and the studios have a close relationship with the censors.

Currently, Thailand's cinemas are subject to the 1930 Film Act, a vague statute that forbids the promotion of bad morals. In practice, that means films dealing with sex, religion and politics are taboo. But violence isn't. That's why you can see plenty of horror movies and comedies in Thailand, but very few political movies. Some film-makers say they have had to pay to get their films passed for exhibition.

The government's justification is that the Thai people aren't educated enough to deal with serious issues. The Ministry of Culture says the average Thai is educated to the level of a sixth-grader [11-year-old] in a US school, and isn't ready for art-house or political movies.

There is a plan to overhaul the 1930 act, but the proposed replacement could be even worse. As it stands, the new bill would introduce a three-tier, age-based ratings system, and the board of censors would retain the power to cut and ban films. The Thai Film Directors' Association and the Thai Film Foundation are against the proposals, but we need more support from the studios and cinemas. However, those two groups have been tempted by the government's promise of a new film fund alongside the ratings system. I doubt that fund, though, will ever be a reality.

Instead of appealing against the banning of Syndromes, I've been lobbying to change the new bill. I believe the government should have no role in the classification of films because Thailand is too corrupt, so I've proposed that we work with the public on constructing and improving the ratings system. And my attempts to change the new bill mean that I now know far more about how politicians think; and I have learned more about how film-makers are treated in Thailand and the obstacles we all face. In fact, my next film will be inspired by what has happened to me.

There will be those who wonder why this matters; why an independent film-maker's movie getting shelved should be of concern to anyone. It's because what happens in the film industry shows us more than how the board of censors works. It shows us how Thailand works. And that really is important.

· Interview by Phil Hoad. Syndromes and a Century is released in the UK on September 21